Field of the Invention
The present invention relates to a sail for a wind-powered vehicle such as surfboard, sailing boat or the like.
Sails for vehicles of the kind mentioned above are widely known and there are several embodiments regarding their size and form. According to the wind situation although with a single vehicle a sail of an adapted size may be used in order to reach a high velocity at the one hand, and to diminish the danger of capsizing as far as possible. It is usual for sailing boats to reef the sailing area of the sail when required, i.e. to move the total sail downwards in relation to the mast, and to roll or fold the lower area of the sail. It is usual for sails of surfboards to use several differently sized sails for a single surfboard which are used according to the wind situation. A change of the sail area during the usage, however, is difficult and impractical.
A surfing sail is known from WO 91/11361 comprising a base sail which at its front edge is connected to a mast which in a usual manner can be connected to a bifurcate boom, and at its clew is connected to the other end of the bifurcate boom, and an additional sail serving for the reefing operation. The additional sail has a triangle shape and is cut narrow and high, and is pivotally connected at its head in the upper area of the base sail adjacent to the rear edge thereof, and in the lower area approximately at the level of the bifurcate boom is provided with a guiding web which is arranged and bent such that it is pivoted at a circular path when pivoting the additional sail with the circular path in the radius thereof corresponding with the distance of the guiding web from the fastening point where the additional sail is secured at the base sail. The guiding web is displaceable in the length thereof such that the additional sail may be pivoted inwards and outwards during the surfing.
With this surfing sail, the sail area is variable, however, there is the great disadvantage in practical operation that when varying the sail area this is accomplished for practical reasons only in the lower area shortly above the bifurcate boom. Thereby, at each variation of the sail area the center of area and thereby the pressure point of the sail is displaced upwards which results in a more difficult handling of the sail by the surfing person. A further disadvantage is that, close to the peak of the sail, a pivoting joint is required which in this area of the sail requires a corresponding rigidity which may be only attained by designing the mast in the peak thereof relatively rigid. Furthermore applications, in this case the pivoting joint in the peak area of the mast have a very negative influence on the weight distribution. The handling of the sail is better if the mast and sail are lighter in the top area thereof. Because of the lever forces which are caused by relatively large mast lengths modern sails in particular surfing sails and masts are made especially light in the top area. During the last years almost exclusively modern masts are used which comprise a so called flex dynamic, i.e. a strongly flexible mast top which yields when the wind pressure raises suddenly, and which thereby automatically decreases the sail area exposed to the wind for a while. This flex dynamic in modern sails is additionally supported by a sail top which is stiffened by sail laths and which comprises a twist dynamic which corresponding with the flex dynamic of the mast deforms the sail top area when the flexible mast top yields, and thereby decreases the sail area without the sailor or surfer having to operate it himself. The use of a mast with flex dynamic, and also the use of a sail with twist dynamic are not possible with the sails known from WO 91/11361 because of the construction.
Furthermore a surfing sail is known from GB 2 235 671 A wherein an adjustable sail part may be displaced upwards and downwards in parallel with the mast. The displacement of the adjustable sail part is attained by cable control with at least one of the cables guided over the top of the mast, and a deflection roller positioned there for pulling the adjustable sail part upwards, and in parallel with the mast, and securing it there by this cable control when the maximal area of the sail is required. For receiving the resulting forces with the deflection roller at the mast top the mast has to have a large stability and rigidity up to its top which results therein that with this known surf sail no mast with a flex dynamic in its upper area may be used. If somebody uses this known sail at a modern mast with a flex dynamic the disadvantage would result that the mast top with the full area of sails would be too soft, and with a small area of sails would be too hard considering the twist dynamics explained above. A change of the front edge length cannot be transferred to modern sails with a twist dynamic.
It is the object of the present invention to provide a generic sail wherein in a simple fashion a variation of the sail area is possible without having a negative influence on the sail characteristic, and which is suitable for a use with modern flex dynamic masts with a flexible upper mast end area without any restrictions. Therein the sail is to be used with sailing boats and catamarans as well as with surfboards and other wind-powered vehicles.
According to the invention the object is attained with a generic sail characterized in that the adjustable sail part can be displaced substantially perpendicular to the free rear edge of the sail and/or substantially parallel to the boom.
Specifically, the sail of the present invention can be connected along its front edge to a mast wherein the sail at its clew or at or near its lower edge can be connected to a boom which is connected in a hinged manner to the mast. In the region of its free rear edge, the sail comprises at least one sail part which is adjustable in the sail plane by moving the sail part laterally in its adjusting direction. As a result, the total surface area of the sail can be decreased by moving the sail part towards the mast or the total area of the sail can be increased by moving the sail part away from the mast.
According to the invention it is advantageously provided to decrease or increase the sail in a simple fashion and even during the use of the associated vehicle in order to adapt the sail area to the wind conditions met. As only a displacement of the displaceable sail part is required for varying the sail area the handling is very simple which makes the new sail usable in particular for surfboards. As the displacing direction of the adjustable sail part substantially extends perpendicular to the free edge of the sail, or in parallel with the boom, respectively, which is substantially in horizontal direction the largest relative area variation of the sail may be attained with relatively small displacement distances. According to the invention advantageously the length of the front edge of the sail remains unchanged such that without any problems a flex dynamic mast, e.g. of carbon material may be used wherein the flex dynamic thereof is unchanged by the embodiment of the sail with an adjustable size. Furthermore the sail area, when adjusting the adjustable sail part, is changed only at the level of the bifurcate boom but for practical reasons is uniformly decreased or increased across the total altitude of the sail and the pressure point of the sail is only slightly displaced backwards or forwards in horizontal direction but in no case upwards or downwards such that the sail characteristic is almost unchanged which is important for handling the sail. Simultaneously, the sail top area remains unchanged which is so important for the flex dynamic and twist dynamic. A sail wherein the pressure point would be displaced upwards when increasing the sail area would require larger holding forces when compared with a sail with a lower sail pressure point which is very disadvantageous in particular in critical situations e.g. when turning the boat or in gust winds because the sail would not perform in a way the sailor or surfer is used to. This disadvantage is completely avoided with the sail according to the invention.
Furthermore it is proposed that in the sail several guiding profiles are arranged in parallel with each other, extending in the displacing direction, and simultaneously serving as sail laths, and that in the guiding profiles several displacing webs are guided which are connected to the displaceable sail part. By this construction it is attained that the displaceable sail part at the one hand may be displaced with small effort, and that at the other hand the sail in total and the displaceable sail part in particular are sufficiently form stable as such and perform as an integral sail when used.
In order not to limit the size of the adjustable sail part to an area above the boom, in particular with a surfing sail, and in order to use the boom for the displacement of the adjustable sail part is proposed that the boom substantially extends in parallel with the guiding profile, and is designed variable in length in its end area facing away from the mast. Bifurcated booms which are variable in length are known especially for surfboard sails, however, only in connection with several sails, each with a firm sail area.
Furthermore it is proposed that in the upper end area of the sail at least one sail lath with a firm length is provided, and that the adjustable sail part extends upwards to the first guiding profile as counted from upwards down. In this way the upper end area of the sail is not dependent from the position of the adjustable sail part in size thereof. This results in the advantage that when using a mast with flex dynamic, i.e. with an especially flexible upper end area the cooperation of the upper sail area with twist dynamic and the flexible mast end is not impaired. Thereby the sail will react independent from the present position of the adjustable sail part when the wind suddenly freshes-up in a way which is used to the sailor or surfer such that the handling of the sail is not impaired.
In an embodiment, the present invention provides a sail assembly for attachment to a mast. The sail assembly comprises a sail comprising a front edge, a rear edge and a clew. The front edge of the sail is connected to the mast. The clew is connected to a boom. The boom is hingedly connected to the mast. The sail defines a sail plane having a total area. The rear edge of the sail comprises at least one adjustable sail part which is adjustable in the sail plane by way of adjusting the longitudinal position of the adjustable sail part in a first adjusting direction substantially parallel to the boom lath and towards the mast wherein the area of the sail plane is decreased and by adjusting the lateral position of the adjustable sail part in a second adjusting direction substantially parallel to the boom and away from the mast wherein the area of the sail plane is increased.
In an embodiment, the sail comprises a plurality of guiding profiles disposed parallel to each other and the boom and extending along the sail in the adjusting direction. The adjustable sail part comprising a plurality of displacing webs disposed parallel to each other and the boom and extending along the adjustable sail part in the adjusting directions. The guiding profiles serving as sail laths. Each guiding profile accommodating at least one displacing web.
In an embodiment, the boom comprises an extendable rear end for increasing the length of the boom along the second adjusting direction.
In an embodiment, the sail further comprises an upper end area. The upper end area of the sail comprises at least one sail lath. The plurality of guiding profiles further comprising an uppermost guiding profile disposed below the sail lath of the upper end area and below the upper end area. The adjustable sail part extending upwards to the uppermost guiding profile.
In an embodiment, each guiding profile accommodates two displacing webs. Each guiding profile comprises a cross beam disposed between two opposing end sections. The cross beam is disposed generally perpendicular to the sail plane and to the end sections. The end sections are bent towards each other and from two profiled longitudinal slots with a cross beam disposed therebetween. Each profiled longitudinal slot accommodates one of the displacing webs of the adjustable sail part.
In an embodiment, the adjustable sail part comprises a rear edge and the displacing webs of the adjustable sail part are arranged in pairs. Each pair of displacing webs is accommodated in one of the guiding profiles on opposing sides of the cross beam. Each pair of displacing webs is connected to one another at the rear edge of the adjustable sail part.
In an embodiment, the guiding profiles comprise a T-shaped cross section with a cross beam that extends perpendicular to the sail plane and which is disposed between the sail and an end section that extends parallel to the sail plane. The displacing webs comprise a C-shaped cross section and the end section of each guiding profile is slidably captured in one of the C-shaped cross sections of one of the displacing webs.
In an embodiment, the sail comprises two plies and forms a pocket between the two plies. The adjustable sail part is extendable in the first adjusting direction where the adjustable sail part is pushed into the pocket and in the second adjusting direction where the adjustable sail part is retracted from the pocket.
In an embodiment, the guiding profiles and displacing webs are fabricated from plastic. The sail and the adjustable sail part are heat bonded or welded to the guiding profiles and displacing webs respectively.
In an embodiment, the adjustable sail part may be locked into an inward position and into an outward position by a releasable locking mechanism.
In an embodiment, the releasable locking mechanism comprises snap-in elements attached to the guiding profiles and displacing webs.
In an embodiment, the guiding profiles comprise rear ends. The releasable locking mechanism comprises manually adjustable clamping elements which are attached to the rear ends of the guiding profiles.
In an embodiment, the sail comprises two plies, folded front edge, two rear edges (one for each ply) and a clew. The sail defines a pocket between the two plies. The front edge of the sail is connected to the mast. The clew of the sail is connected to the boom. The boom is bifurcated or, includes two rearwardly extending legs, an extends along each ply of the sail. The sail defines a sail plane having a total area. The rear edges of the sail are connected to at least one adjustable sail part which is adjustable in the sail plane in one of two directions by adjusting the longitudinal position of the sail part in a first adjusting direction substantially parallel to the boom and towards the mast wherein the adjustable sail part moves into the pocket defined by the two plies of the sail in the area of the sail is decreased and, by adjusting the lateral position of the adjustable sail part in a second adjusting direction substantially parallel to the boom and away from the mast wherein the adjustable sail part is retracted from the pocket and the area of the sail plane is increased.
In an embodiment, the plies of the sail are connected by a plurality of guiding profiles disposed parallel to each other and the boom and which extend along the plies of the sail in the adjusting direction. The adjustable sail part comprises a plurality of displacing webs disposed parallel to each other and the boom and extend along the adjustable sail part. The guiding profiles serving as sail laths; each displacing web being accommodated in one guiding profile of each ply thereby connecting the two plies together.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.
Preferred embodiments of the guiding profile and the displacing webs guided therein are stated in the claims 5, 6 and 7. The embodiments described there at the one hand provide a low weight of the guiding profiles and displacing webs, and at the other hand a high stability.
In order to exclude that between the stationary parts of the sail and the adjustable sail part slots are formed which let the wind pass with the slots decreasing the effect of the sail as far as the propulsion of the vehicle is concerned it is provided that the sail at least in an area wherein the displaceable sail part is positioned with minimal sail area is designed double ply in form of a pocket wherein the displaceable sail part may be pushed into this pocket, and retracted from this pocket.
To attain a weight of the sail as low as possible, and for simultaneously guaranteeing high stability and rigidity it is proposed that the guiding profiles and the displacing webs are manufactured of plastic material, and that the sail cloth of the stationary part of the sail is connected with the guiding profiles, and the sail cloth of the displaceable part of the sail is connected with the displacing webs, preferably bonded or welded.
To enable the adjustment of the displaceable sail part with as little effort as possible, and simultaneously to exclude a non-required displacement of the displaceable sail part it is provided that the displaceable sail part at least in its two end positions in relation to the remaining sail is to be secured by means of releasable locking means.
The locking means mentioned above e.g. may be cooperating snap-in elements at the guiding profiles and displacing webs, and eventually at the parts of the boom displaceable in longitudinal direction towards each other, or alternately may be manually adjustable clamping or locking elements which are arranged at the guiding profiles preferably at the ends facing the free edge of the sail, and eventually at the displaceable parts of the boom to be displaced in relation to each other in longitudinal direction.